This invention is an improvement of Applicant's single cartridge filter as disclosed in U.S. Pat. No. 4,561,979, issued Dec. 31, 1985, which is incorporated by reference herein. The improvements and benefits derived from this invention are best understood in relation to this single cartridge filtering system.
The single cartridge filtering system comprises a housing having a removable domed cover and a horizontal partition in the housing to form separate filtered and unfiltered liquid chambers. A large vertical cylindrical pleated filter cartridge is suspended from the lower side of the partition in the unfiltered liquid chamber of the housing.
The filter cartridge has a central perforated tube which fits over and is radially spaced from a vertical outlet tube. The outlet tube extends out from the bottom of the housing to an aperture in the partition. This partition aperture forms an annular opening for allowing passage of filtered liquid from the interior of the filter cartridge into the clean liquid chamber in the domed cover. The lower end of the filter cartridge seals to a threaded male adapter around the bottom of the outlet tube. An annular pleated filter sleeve surrounds the perforated tube.
In the single cartridge filtering system, the liquid to be filtered enters the housing below the partition. After passing through the filter media and the perforated tube, the filtered liquid travels upwardly around the outside of the outlet tube into the clean liquid chamber and then down through the outlet tube.
The structure of the single cartridge filter system causes gases in the filtered liquid to accumulate in the clean liquid chamber below the domed cover. The flow of filtered liquid into the domed area and down the outlet tube displaces the collected gases, forcing the gases down the outlet tube. This automatic removal of the gases results in an increased efficiency of the filtering system by preventing accumulated gases from occupying a large volume of the filter region. Additionally, the single cartridge filtering system provides a means for easy removal of the filtering cartridge.
Although the single cartridge filter system provides means for improved filtration efficiency over other filtering systems, the single cartridge filter system does not prevent two causes of decreased filtration efficiency.
The first cause of decreased filtration efficiency in the single cartridge filtering system results from a reduction of filter media surface area, referred to as blinding off. The filtering media of the single cartridge comprises an annular sleeve of filtering material, such as paper, which is pleated to provide a maximized amount of surface area for filtering. During the filtering process, the force imparted on the filtering media by the fluid flow causes several of the pleats to be compressed together, thereby reducing the total effective surface area for filtering. One method for reducing this blinding off is to provide reinforcement rings circumferentially along the length of the filtering media. However, these reinforcement rings do not completely prevent the blinding out of the pleated media. Another cause of reduction in filtration efficiency is the clogging of the filtration media by particles which are transported into the system by the fluid to be filtered.